Things You'll Need
20 lbs. fresh San Marzano tomatoes
7 oz. bottled lemon juice
Large mixing bowl filled with cold water
14 pint-sized canning jars with lids and rubber ring seals
Pressure canning machine
San Marzano tomatoes are often considered the ideal tomatoes for making sauce. San Marzano tomatoes are thinner than Roma tomatoes (a common variety of tomato), with a pointed end. They bear thick flesh with few seeds, making them ideal for canning and cooking. Their flavor is strong, sweet, and less acidic than other varieties of tomato. When canning San Marzano tomatoes at home, it is important to use a pressure canner, as it kills more bacteria than boiling water and provides a more sterile product.
Prepare the tomatoes for canning
Place the jars and lids in the dishwasher to sanitize them. Washing them in one cycle is sufficient for sterilization.
Place a large pot on the stove, and turn heat to medium-high. When the water comes to a boil, drop in tomatoes. (Do this in batches, if necessary.) Let the tomatoes boil until the skins begin to blister; this indicates that are ready to be peeled.
Drain the tomatoes using a colander, and place them in the large bowl filled with cold water. Once they are cool, remove the tomatoes from the water and peel and core them using a paring knife. As the tomatoes are peeled, place them back into the pot in which you boiled the water.
Add the lemon juice to the tomatoes in the pot on the stove. Heat the pot to medium-high heat. Heat the peeled tomatoes until they are warmed through, approximately five minutes.
Spoon the tomatoes into pint jars. Leave approximately 1/2 inch space toward the mouth of the jar. Place the lids on jars and secure tightly with the rubber rings.
Seal and sterilize the jars
Place filled pint jars into the pressure canner. Follow the instructions included with the canner and set the appropriate pressure and heat level. When that level is reached, allow the tomatoes to remain in the canning machine for 20 minutes.
Remove the pressure canner from heat and allow it to cool. Once it has cooled, follow the manufacturer's directions for removing the lid. Pull the lid off the canner away from your face, as the canner will release a burst of hot steam.
Remove the jars from the pressure canner using the jar lifter (included in most pressure canners) or a set of tongs. Set the jars aside and allow them to cool for 12 to 24 hours. As the jars cool, you will hear a popping sound; this indicates that a tight seal has formed and the tomatoes will be preserved according to food-safety standards.
Store tomatoes in a cool, dark place. They will keep up to a year when stored out of direct sunlight.
This recipe yields approximately seven quarts of canned tomatoes. The ingredient measurements can be adjusted depending on the amount of tomatoes you plan to can.